Releasable closure

ABSTRACT

A detachable closure includes separable burr-type elements which, at surfaces to be joined, have interlocking elements which mutually interlock during joining of the burr-type elements and hold the burr-type elements together. The interlocking elements are made of a material which carries out a deformation under the influence of heat, electromagnetic radiation, and/or a magnetic field.

BACKGROUND

The present invention relates to a detachable closure made of separableburr-type elements which feature interlocking elements at the surfacesto be joined, the interlocking elements mutually interlocking during thejoining of the burr-type elements, holding the burr-type elementstogether.

In many fields of technology, detachable closures are used tonon-permanently interconnect parts. In this manner, the possibilityensues for parts to be firmly fixed but nevertheless to be detachedagain.

Known from U.S. Pat. No. 2,717,437 is a detachable closure which iscomposed of two burr-type elements which feature a large number offlexible interlocking elements which interlock with each other when theburr-type elements are pressed together. In this manner, a multitude ofconnections ensues between the interlocking elements of the twoburr-type elements, resulting in a strong mutual fixation of theburr-type elements. This type of closures is also known as a Velcroclosure and is used in the field of the clothing industry.

It turns out to be a disadvantage of detachable closures of that kindthat the connection can only be detached by stripping off the burr-typeelements from each other and in that shear forces act upon theinterlocking elements. The elastic design of the interlocking elements,on one hand, prevents the interlocking elements from being released outof the burr-type elements in the process and, on the other hand,supports the separation. Thus, the interlocking elements can be bentopen to let opposite interlocking elements slip out of the interlockingconnection. In a closure of this kind, the connection can only beseparated if at least one of the components to be joined is flexurallysoft or if the components can be sheared off from each other. Aseparation of the components in a direction perpendicular to thesurface, as occurs in the case of flexurally stiff components whichcannot be tilted relative to each other, is only possible with anexcessive expenditure of force which mostly destroys the detachableclosure at the same time.

German Patent Document 196 48 254 describes a pressure closure strapwhich has two matching profiles and in which at least one profile halfof the pressure closure strap is intentionally designed to beself-destructive. The destruction of at least one half during theseparation of previously joined strap halves has as a result that arepeated use is not possible. The self-destruction can be attainedeither via predetermined breaking points at the tops of the profile ribsgripping behind each other or by elastomers which have a shape memoryand which, after being put together, are shrunk so as to interlock, andwhich, during separation, take on a shape which prevents a repeatedclosure.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a detachable closurethat can be detached in a controlled manner without using large shearforces. Moreover, an object is for the interconnection to be separablein a direction perpendicular to the surface.

To attain this objective according to the present invention, adetachable closure of the type mentioned at the outset is characterizedin that the interlocking elements are composed of a material whichcarries out a deformation in response to the influence of heat.

Using the closure according to the present invention, it is possible forthe components which are held together therewith to be detached withouthaving to apply shear forces via stripping abrading movements. Thisallows the components to be lifted off in the direction of the surfacenormal. Besides, it is no longer required that one component beflexurally soft. Secondly, due to the possibility of detaching theinterlocking connection in a defined manner, the required expenditure offorce is reduced to a minimum since it is no longer necessary to applyenergy for deforming the elastic interlocking elements until the finalseparation.

The heat can be introduced into the interlocking elements by indirectlyheating the components or the burr-type elements. Advantageouslyhowever, the heat is brought about by current flowing through theinterlocking elements to be changed. The resistance offered to thecurrent flow by the interlocking elements causes the current to beconverted into Joulean heat, resulting in the heating of the elements.This heating causes the shape of the interlocking elements to open.

According to the present invention, the set objective can also beachieved in that the interlocking elements are composed of a materialwhich carries out a deformation in response to the influence ofelectromagnetic radiation.

In both design approaches, bimetals or expansion material elements canbe used as materials for the interlocking elements. In a preferredembodiment, however, the interlocking elements are composed of a shapememory alloy. Compared with conventional structured materials, shapememory alloys additionally offer special properties which make itpossible to use them in the mentioned environment. Due to the capabilityof remembering a specific shape in the low-temperature martensite phaseand in the high-temperature austenite phase, it is possible fordeformations to be achieved over a previously set temperature range overa large number of cycles.

In connection with the austenitic-martensitic phase transformation andthe associated deformation, it is possible to take advantage of twoeffects. Via the one-way effect, an interlocking element made of a shapememory alloy which was bent closed, i.e., plastically deformed, in thetemperature range in which the alloy exists in the martensitic phase,begins to open again when it is heated beyond the temperature at whichthe transformation into the austenitic phase begins. The alloy begins to“remember” the original shape so that a deformation is carried out in acontrolled manner via heat supply, detaching an interlocking connection.In this manner, it becomes possible for the detachable connection to beopened one time in a controlled manner in the desired form.

It is advantageous to impress reshapings on the interlocking elements ofshape memory alloys via a so-called “training” which allows theinterlocking elements to remember a specific shape both in theaustenitic phase and in the martensitic phase. In this context, an openinterlocking element and a closed interlocking element are conceivable.To this end, dislocation structures are impressed on the interlockingelement made of a shape memory alloy by deforming the alloy beyond themartensite plateau. These dislocation structures restore the alloy tothe desired shape also during cooling. In this manner, the detachableconnection can be cyclically detached or joined several times byincreasing or reducing the temperature of the interlocking elements,depending on the requirements. Thus, not only a controlled detachmentbut also an active joining becomes possible if required by thecircumstances as is the case, for instance, subsequent to an exactpositioning of the components.

Shape memory alloys which can be used for the interlocking elementsinclude a plurality of materials such as special alloys of copper, zincand aluminum or iron, manganese and silicon. Here, the use depends onthe temperature range in which the detachable closure is intended to beused and on the temperature at which the deformation begins and, thus,at which the detachment of the closure is accomplished. Advantageouslyhowever, the shape memory alloy is composed of a nickel titanium alloywhich is composed of 49.9 atom % of nickel and 50.1 atom % of titanium.The advantage of this alloy lies in the commercial availability, thelarge operating-temperature range, and in the large number of thermalcycles that can be performed with this material.

According to an embodiment of the present invention, the interlockingelements are composed of a material which carries out a deformation inresponse to the influence of electromagnetic fields.

Used as materials for this purpose are, in particular, electro- andmagnetostrictive solid bodies as, for example, piezoelectric ceramics orpolymeric materials.

Preferably, the interlocking connection of the interlocking elements iseliminated by the degree of the deformation resulting from the influenceof heat, electromagnetic radiation and electromagnetic fields. In thiscontext, the regions of the interlocking elements which offer resistanceto the opposite interlocking elements of the other burr-type elementsand which thus bring about the connection are changed to the extent thatthe interlocking elements can be separated from each other without muchexpenditure of force.

The shape of the interlocking elements is to be selected in such amanner that it is ensured that the interlocking elements of the twoburr-type elements mutually interlock during the joining, thus fixingthe burr-type elements relative to each other. Preferably however, theinterlocking elements of one burr-type element are hook-shaped and thoseof the other burr-type element are loop-shaped. An embodiment of thatkind ensures a particularly easy interlocking as the burr-type elementsare pressed together since the hook-shaped interlocking elements easilyentangle in the loop-shaped interlocking elements, resulting in themutual fixation of the elements and, thus, in the union. However, it isalso possible to attach hook-shaped interlocking elements on both sidesof the burr-type elements, the hook-shaped interlocking elementsmutually interlocking.

Preferably, the number of loop-shaped interlocking elements per surfaceunit on one burr-type element is larger than the number of hook-shapedinterlocking elements on the other burr-type element. In this manner, itis ensured that as the burr-type elements are brought together, a largenumber of hook-shaped interlocking elements find a companion, that is tosay a loop-shaped interlocking element to secure the connection betweenthe burr-type elements in the best possible manner. In this manner, theforce required for an unwanted separation of the burr-type elements ismaintained at as high a level as possible. This force is a measure forthe quality of the detachable closure since the detachable closure mustbe protected against unwanted detachment due to influences of externalforces.

In a particularly preferred embodiment, the deformation of theloop-shaped interlocking elements which causes a detachment of theinterlocking connection consists in the formation of a gap so that aninterlocking element of the opposite burr-type element entangled thereincan slip out. This gap formation is preferably attained in that the loopwings forming the loop are abutted on each other at an obtuse angle orin that they overlap each other in the region of the gap to be formedand in that they move away from each other during the deformation so asto form the gap. In the case of the hook-shaped interlocking elements,the deformation which causes the detachment of the interlockingconnection is an elongation of the hook bow so that an interlockingelement of the opposite side entangled therein can be drawn off withoutexpenditure of force.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be explained in greaterdetail by way of an exemplary embodiment depicted in drawings from whichfurther details, features and advantages can be gathered.

FIG. 1 shows a schematic representation of two interlocking elements inthe unclosed condition;

FIG. 2 shows the interlocking elements during the formation of adetachable closure;

FIG. 3 shows the closure during active detachment or during activejoining.

DETAILED DESCRIPTION

The system schematically shown in FIG. 1 is a cross-section through adetachable closure 1 which, in the present case, is composed of twoburr-type elements 10, 20. Burr-type elements 10, 20 include two sheetstructures 11, 21 and interlocking elements 12, 22, the interlockingelements being formed on first burr-type element 10 in the form of loopsand on second burr-type element 20 in the form of hooks.

In the specific embodiment represented here, first burr-type element 10possesses a higher quantity per unit area of loop-shaped interlockingelements 12 than the quantity per unit area of hook-shaped interlockingelements 22 at second burr-type element 20. In this manner, it isensured that all hook-shaped interlocking elements 22 entangle at leastin one loop-shaped interlocking element 12, thus mutually fixing theburr-type elements and augmenting the expenditure of force required forthe unwanted detachment of the closure. The entire first burr-typeelement 10, sheet structure 21 is also manufactured from a polyamidefiber in that, during a weaving process, numerous small loops are pulledout of sheet structure 11, forming loop-shaped interlocking elements 12.In second burr-type element 20, sheet structure 21 is also composed of awoven polyamide fiber in which a wire made of a nickel-titanium alloywas woven during the manufacturing process in such a manner that,initially, loops are formed which project above the burr-type elementand which, in a subsequent process, are cut open on one side so as toform hook-shaped interlocking elements 22. Here, a cutting in the middlewould also be conceivable. The alloy wire has a diameter of 0.2 mm andis composed of 49.9 atom % of nickel and 50.1 atom % of titanium. Thismaterial is a shape memory alloy and is known for the fact that itundergoes a deformation during the transition between the martensiticand austenitic phases which is used here for opening the interlockingelements. However, interlocking elements 20 can also be composed ofother shape memory alloys so that the detachable closure can be adaptedto different temperature ranges. Likewise, it is possible to use adifferent fiber for burr-type element 10 and sheet structure 21 in lieuof the polyamide fiber used here. On the whole, other materials andmanufacturing methods are, of course, possible as well. Thus, it ispossible for sheet structures 11, 21 to be formed of a plastic plate andfor interlocking elements 12, 22 to be cast in. Likewise, it isconceivable for interlocking elements 11, 22 to be introduced directlyinto the surfaces of the components to be joined so as to integrate thesheet structures into the components and save costs. Moreover, it ispossible for loop-shaped interlocking elements 12 to be composed ofmetal or a metal alloy. This information is to be regarded as being onlyexemplary but not as a limitation of the present invention.

When the two burr-type elements 10, 20 are pressed together, hook-shapedinterlocking elements 22 interlock with loop-shaped interlockingelements 12 as is depicted in FIG. 2. If burr-type elements 10, 20 areattached to two components via sheet structures 11, 21, the componentsare joined in this way. Due to their material, hook-shaped interlockingelements 22 are fluxurally stiff so that a separation of the componentsat this stage can only be accomplished with extremely large expenditureof force and only via shear forces transverse to the surface.

FIG. 3 shows the detachment process which, in the present exemplaryembodiment, is induced by heat radiation up to a temperature ofapproximately 90° C. In this context, two effects can be taken advantageof.

In the case of the so-called “one-way effect”, the shape memory alloywhich was pseudoplastically deformed in the martensitic structureremembers its original shape when heated and returns to its undeformedcondition during the transition to the high-temperature austenite phase.The plastic deformation mentioned here gets into hook-shapedinterlocking elements 22 during the weaving process when a loop whichwill later be cut open is formed from the originally straight alloywire. Of course, the deformation can also be brought in in a differentmanner, depending on the manufacturing process. In the case of theone-way effect, the alloy, and thus hook-shaped interlocking elements22, does not change its shape again so that the connection cannot beclosed any more and is usable only once unless hook-shaped interlockingelements 22 are deformed again via an external force, for example, asburr-type element 10, 20 are pressed together.

Via the so-called “two-way effect”, it is possible for the connection tobe detached as described for the one-way effect and also to be reusedfor further connections. Possible is, moreover, an active joining. Thetwo-way effect describes the fact that a shape memory alloy is capableof remembering both a specific shape in the high-temperature austenitephase and one in the low-temperature martensite phase. In thisconnection, the transformation is impressed on the shape memory alloy byseveral load cycles, the so-called “training”. In the process, the alloyis deformed in the martensitic phase beyond the martensite plateau so asto bring in plastic deformations by dislocations as well. Due to thedislocations, only part of the deformation component disappears duringheating. During cooling, the existing plastic stress fields around thedislocations give rise to martensite variants which transform the alloyinto the desired low-temperature shape. Here too, the deformation beyondthe martensite plateau is brought into interlocking elements 22 duringthe weaving process.

By using this effect, it is possible for the connection to be detachedvia heating in that hook-shaped interlocking elements 22 stretch duringheating. When cooling, hook-shaped interlocking elements 22 form back sothat a further joining operation is possible. However, burr-typeelements 10, 22 can also be joined with hook-shaped interlockingelements 22 being open and then be cooled as a result of which anactive, multidimensional joining is possible.

Of course, the one-way or two-way effects can be used analogously if, inplace of hook-shaped interlocking elements 22, loop-shaped interlockingelements 12 open and release the connection or if hook-shapedinterlocking elements 22 are used on both burr-type elements 10, 20.

Via the mentioned means, a joining which is known form the Velcroclosure is possible which brings about a very strong bond between thecomponents to be joined.

In addition, however, the separation of the components is achievedactively by radiation of heat as a result of which no force needs to beapplied for the separation and the need for the shear motion of thecomponents to be detached is eliminated.

What is claimed is:
 1. A detachable closure comprising: a firstburr-type element including a plurality of first interlock elements; anda second burr-type element including a plurality of second interlockelements; wherein the plurality of first and second interlock elementsare configured for mutually interlocking during a joining of the firstand second burr-type elements so as to separably hold the burr-typeelements together; and each of the plurality of first and secondinterlock elements includes a respective material which deforms inresponse to as least one of heat, electromagnetic radiation, and anelectromagnetic field so as to disestablish the interlocking of theplurality of first and second interlock elements.
 2. The detachableclosure as recited in claim 1 wherein each of the plurality of first andsecond interlock elements includes a respective resistance heater. 3.The detachable closure as recited in claim 1 wherein each of theplurality of first and second interlock elements includes a respectiveshape memory alloy.
 4. The detachable closure as recited in claim 3wherein each of the respective shape memory alloy has a respective formin which plastic deformations exist via dislocations in a respectivegrain structure.
 5. The detachable closure as recited in claim 3 whereinat least one of the respective shape memory alloy includes 49.9 atom %of nickel and 50.1 atom % of titanium.
 6. The detachable closure asrecited in claim 1 wherein the plurality of first interlock elements arehook-shaped and the plurality of second interlock elements areloop-shaped.
 7. The detachable closure as recited in claim 6 wherein anumber of the plurality of second interlock elements per unit surfacearea is larger than a number of the plurality of first interlockelements per unit surface area.
 8. The detachable closure as recited inclaim 6 wherein the deforming of the respective material included ineach of the plurality of second interlock elements causes a forming ofrespective gaps and the deforming of the respective material included ineach of the plurality of first interlock elements causes respectiveelongations.
 9. The detachable closure as recited in claim 6 wherein thedeforming of the respective material included in each of the pluralityof first and second interlock elements causes respective elongations.10. The detachable closure as recited in claim 7 wherein the deformingof the respective material included in each of the plurality of secondinterlock elements causes a forming of respective gaps and the deformingof the respective material included in each of the plurality of firstinterlock elements causes respective elongations.
 11. The detachableclosure as recited in claim 1 wherein the plurality of first and secondinterlock elements are hook-shaped.
 12. A method for detachablyconnecting a first component to a second component, the methodcomprising: undetachably disposing a first burr-type element on thefirst component, the first burr-type element including a plurality offirst interlock elements; undetachably disposing a second burr-typeelement on the second component, the second burr-type element includinga plurality of second interlock elements; and joining the first andsecond burr-type elements so as to interlock the plurality of first andsecond interlock elements and separably hold the burr-type elementstogether, each of the plurality of first and second interlock elementsincluding a respective material which deforms in response to as leastone of heat, electromagnetic radiation, and an electromagnetic field soas to disestablish the interlocking of the plurality of first and secondinterlock elements.
 13. A method for detachably connecting a firstcomponent to a second component, the method comprising: providing aplurality of first interlock elements on a first surface of the firstcomponent; providing a plurality of second interlock elements on asecond surface of the second component; and joining the first and secondcomponents so as to interlock the plurality of first and secondinterlock elements and separably hold the first and second componentstogether, each of the plurality of first and second interlock elementsincluding a respective material which deforms in response to as leastone of heat, electromagnetic radiation, and an electromagnetic field soas to disestablish the interlocking of the plurality of first and secondinterlock elements.